holds the potential to store up to 2 MW of energy
2nd paragraph and he's already lost me. It would be nice if tech columnists had the equivalent of even a single semester of high school physics.
this post was submitted on 07 Feb 2024
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I googled Pyhäsalmi Mine gravitricity "2 MW" and EVERY article covering this has also cited 2 MW.
Now, under Occam's Razor, what's more likely:
- Absolutely none of the article writers have any clue what the difference between a MW and a MWh is because none of them remember any physics
- Some of them could suspect that it's wrong, but an authoritative source of the claim wrote/said 2 MW capacity when they meant "2 MW peak generation" or "2 MWh storage" (I'd presume Gravitricity, but I'm struggling to find such a source, myself)
- One writer miswrote/misquoted as per 2, and everyone is mindlessly recycling that original article's contents with no attribution or care.
I don't know which one it is. But I'd generally lean against 1.
#2 is certainly food for thought. So the idea is that from a journalistic fact-checking point of view, it is more important to convey the information exactly as it was presented than to verify its accuracy?
This would explain why science/engineering-based articles are so commonly inaccurate or missing in critical details. The journalist can fall back on saying "I have a recording of an interview with the expert after we downed a few pints at the pub, and I'm just parroting back what he said. Don't shoot the messenger!"
I'd honestly prefer raw parroting in most cases, even if it's "obviously" wrong. I don't want people selectively interpreting the facts as have been conveyed to them, unless they're prepared to do a proper peer review.
That’s what [sic] is for though. You fact check, and then leave the quote as the press release had it.
The problem is that most of these articles are basically reprinting of the press release without any editorial additions at all.
I'd wager they let bots crawl articles and have said ai bots rewrite them slightly. Internet journalism is completely lost.
Then there's the issue between scientific jargon that is different from general public use. A scientific theory has a specific definition, but it's easy for general population to dismiss them as "just a theory".
Or is all just LLMs summarising the same badly translated source.
Though btw, I also think it's fascinating the difference if you look up Pyhäsalmi Mine gravitricity "2 MW" vs Pyhäsalmi Mine gravitricity "2MW"
You'll get different articles entirely
Mistakes like this could be avoided if we just used joules for energy and watts for power.
Or just joules per second for power. Eliminate watts entirely. Dumbass unit
Well, Watts are just a different way to write Joules per second. The unit we should eliminate is {k,M}W.h which introduce a 3.6 factor in conversions to/from the regular unit system
My fave has gotta be kwh/yr/ft². I came across that while researching the lighting requirements for hydroponics.
Well, it kind of makes sense to give a figure in such an unit. It allows you to quickly calculate how much you're gonna spend on your electric bill (but only if you're based in the US), since all weird conversions are already done
These cursed time units remind me of the super messy imperial units. Unfortunately, the French revolution wasn’t able to fix that, but it did fix a whole lot of other nonsense.
Yeah but if we all wrote "joules per second" instead of watts we'd encourage everyone to measure energy in joules instead of watt-hours. It's like speed, we don't need an entirely separate unit that just means m/s
It's the independent 🤷♂️
Alright, I've been to high school but never understood "Wh". For speed we say "They are moving at 25 km/h aka 25km per hour" --> in one hour the object will have traveled 25km. per indicates division. Same for flow rate (cubic meters per second --> l/s) --> "The swimming pool of 5m³ was filled at 0.5m³/h and took 10h to fill".
If something generates or consumes 10W per hour, shouldn't that be 10W/h not 10Wh? If I hold an object that weighs 100g for an hour, doesn't that mean I have been exerting myself at the gravitational force of the 100g object for 1 hour --> (100g * 9.832m²/s) / h --> (100g*9.832m²/s) / 3600s and thus the units being g * m² * s⁻² which are joules? How does that equate to "watt hours"
Can somebody explain this to me conceptually? It makes no sense to me.
What you're forgetting is that Watt isn't a unit of energy, it's a unit of power, that is energy per time. So you wouldn't say something generates 1W per hour, you'd just say something generates 1W. And if you multiply that by a unit of time, you get total energy. So an engine producing 2MW running for 5h would produce 10MWh, or 36GJ.
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100g * 9.832m²/s
That should be 100g * 9.832m/s², or better yet 0.1kg * 9.832m/s² to get a number in newtons (N).
From a high school physics perspective, holding a 100g object steady for any length of time does no work, since work is force applied over a distance, measured in joules (J). What you do have is gravitational potential energy. Potential energy is the ability to do work, also measured in joules. Once you release the object, then you actually start getting numbers for work and power.
Power, measured in watts (W), is work done per unit time. So 10W/hr would be (10J/s)/hr. I guess that would be the rate of change of power consumption, if that were useful to you?
In theory, energy and work should be measured in joules. Simple as that. But this unit of kwh (kilowatt∙hour) has come into vogue, presumably because that's what power utilities show on the meter outside your house? 1 kW∙hr = 1 kJ/s∙hr ∙ (1000J / kJ) * (3600s / hr) = 3.6MJ. So now we're back from power to energy consumption.
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2MW of energy 🤦♂️
Just walked the distance of 1.8 km/h.
I just waited for 2 light-years at the doctor's office.
I did the kessel run in under 12 parsecs.
2MW is a measure of power, not energy.
Time for something to free fall 1.4km is about 17s, so the minimum capacity is 34MJ or 9.4kWh in order to make their statements true. $1.50 in electricity.
I sincerely doubt this is accurate or why would they even bother.
All solid weight gravity batteries are a scam. The sound good enough to get grant money, but if you run the numbers, they are pitiful batteries.
To make it worth while you need literal lakes of water.
That's so cool!
This is one of those ideas that in hindsight seem so simple and obvious that it makes one wonder how nobody thought of it prior. Absolutely brilliant.
Because it's super inefficient
Not if the energy would go to waste. This is a mechanical battery to store surplus power generation from things like wind and solar.
It wouldn't go to waste if we were to use "gravity batteries" that have existed for centuries: hydropower
That’s the whole point of grid energy storage. Even if there are losses, it’s acceptable considering that otherwise you would need to burn fossil fuels in a peaker plant to keep the grid balanced. You aren’t supposed to recharge a battery like this with fossil fuels.
Is it more or less efficient than a derelict mine and an unstored energy surplus?
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Very interesting, and good to hear.
Though, I'm not sure why they would drive a turbine to drive a generator, instead of just driving the generator directly. Their illustration doesn't show any turbines either.
Just guessing here but I think they are playing with gear ratios. A large turbine with high resistance being slowly turned by a heavy weight could generate power for an extended period of time.
EDIT: Maybe the shaft is the turbine. Like a big rotating corkscrew.
And that's my confusion, why use a turbine (connected to a lift) to turn the heavy weight into a flow of steam or liquid, presumably to convert this flow to electricity using another turbine with a generator connected to it, instead of simply converting the heavy weight to electricity using a lift (or corkscrew) to turn the generator?
This is, of course, assuming that a turbine only is a turbine when it is driven by steam or liquid.
I guess the publishers of the article either got the definition wrong, or there's a less used definition of turbine which I am not aware of.
The turbine is the part that turns potential energy into rotational energy. The generator turns that rotation into electricity.
But isn't the definition of a turbine "a type of machine through which liquid or gas flows and turns a special wheel with blades in order to produce power" with the "power" (aka. rotational energy) going to a generator?
Where does the liquid or gas come from? Isn't this battery supposed to lift heavy, solid objects?
It doesn't outright state that it uses solid weights, but their illustration looks more like they'd use a lift with sand or weights, and not a turbine with liquid or steam:
I wasn't suggesting that a turbine could be used (directly) for sand, I hope you didn't get that impression, I was just trying to address that commenter's point of confusion about generators and turbines.
To your question, a flow is cause by a difference in energy potentials between two connected points in a system; Potential energy causes the gas or liquid to flow through a turbine. The more potential energy, the higher the speed, or pressure (depending). Also, not all turbines drive generators. The output could drive anything where you need rotational input, including a vehicle's transmission. For a lot of reasons, that isn't usually done.
If I understand correctly, the idea is to store something heavy up top, send it down below using the weight of the sand to somehow (unspecified?) generate electricity, then send it back up when there is an excess supply of energy generation, leaving it available to use again when energy production is reduced. Battery really describes this system better than generator, because it's only a hole in which to dump excess energy and then pull it out (which, in a roundabout turn of events, the "hole" in this instance is above ground, and then you "pull it out" of the hole by sending it back down.).
All that said, this seems like a boondoggle. I think there's a lot in this press release that is unsatisfactory, and I'm extremely skeptical that this makes good sense until I see definitive independent proof otherwise.
Right, my bad. I thought you were explaining turbines in relation to the post, which would indeed have one attempt to run sand through it if not used with either liquid or steam.
I also wrote turbine and generator separately, as, as you stated, turbines and generators are not the same. I, in turn, hope I didn't give the impression that they were.
I fully agree about the system as a whole better being described as a battery, which usually includes generators of some sort to convert the stored energy back into electricity.
And yes, this is a rather precarious article, which also is why I wrote the half-question half-joke about unnecessary conversion steps using turbines.
The illustration also showed a bucket wheel excavator. Don’t remember seeing that the last time I visited Pyhäsalmi.
Interesting. Earlier they were planning pumped storage there, with a claimed capacity of 530MWh https://yle.fi/a/3-12593341 Seems like that fell through https://www.epv.fi/en/project/a-pump-storage-station-for-pyhasalmi-mine/
Every source I can find says "2MW" of capacity. I assume they meant 2MWh, though that doesn't sound like that much.
They’re planning to use the 530 m long secondary shaft at first. The entire mine is a lot deeper, so obviously, there are other shafts too. You gotta start somewhere.
I been promoting this shit for a while now. Energy storage can be surprisingly low tech, it just needs to be built